Rice yellow mottle virus disease resistance among diverse rice genotypes
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A diverse collection of 112 genotypes that had been introduced at NaCCRI to improve farmer grown rice genotypes were evaluated against three RYMV isolates from rice fields in Iganga (Eastern Uganda), Lira (Northern Uganda) and Kabanyolo (Central Uganda) which are areas considered to be RYMV “hotspots” in Uganda. The Iganga RYMV isolate was found to be the most virulent isolate and subsequently used to evaluate resistance level of the genotypes by using foliar symptom severity score and percentage grain weight reduction. The response to RYMV highly varied amongst the genotypes. Very few genotypes, however were found to be Highly resistant or Resistant. Genotypes Gigante, ARC36-2-P-2 (2), ARC39-145-P-3 (4), ARC39-145-P-2 (5), ARS126-3-B-1-2 (11) and IRL 53 (GP 54) were found to be Highly resistant while genotypes ARC36-2-1-2 (1), ARC36-4-EP-2 (3), IRL 2 (GP 54), IRL 4 (69 GP 54) and IRL 5 (GP 54) were Resistant when evaluated basing on symptom severity score. Percentage grain weight reduction varied between 0 and 100%. Gigante genotype was had a net gain in grain weight when infected with RYMV while 48.2% of the genotypes lost 100% grain weight and over 80% of the genotypes lost more than 60% grain weight. By coupling grain weight reduction and severity score, only genotypes Gigante, ARC36-2-P-2 (2), ARC39-145-P-3 (4), ARC39-145-P-2 (5), ARS126-3-B-1-2 (11), IRL 53 (GP 54), ARC36-2-1-2 (1), ARC36-4-EP-2 (3), IRL 2 (GP 54), IRL 5 (GP 54) and MET P44 were recommended for further breeding to improve rice genotypes in Uganda.